Diphosphonate compounds, their preparation and application

ABSTRACT

The invention relates to a new compound of the formular (1): ##STR1## wherein m 1  =0, 1 or 2, m 2  =0, 1 or 2, m 1  and m 2  are not to be simultaneously 0 or simultaneously 2; n 1  =2-m 1 , n 2  =2-m 2  ; R=either H or alkyl with 1 to 8 carbon atoms, R&#39;=alkyl with 1 through 18 carbon atoms, and X=H or OH. 
     The invention also relates to the preparation thereof, the compositions containing them and the application in catalysis of oxidation of hydrocarbons, particularly in catalysis of oxidation of cyclohexane.

This is a division of application Ser. No. 07/592,166, filed Oct. 3,1990 now abandoned.

The present invention relates to new diphosphonate compounds.

More particularly, the present invention relates to new kinds ofdiphosphonate compounds, their preparation process, compositionscontaining them and their application.

Accordingly, one of the purposes of the present invention is to providenew and useful diphosphonate compounds.

Another purpose of the present invention is to provide a process formaking the said diphosphonate compounds.

Yet another purpose of the present invention is to provide compositionscontaining the diphosphonate compounds for catalysis.

A further purpose of the present invention is to provide application ofthe said diphosphonate compounds and compositions containing them forcatalysis in oxidation of hydrocarbons, the oxidation of cyclohexane, inparticular, etc.

The diphosphonate compounds of present invention are novel and may bedesignated by the following general formula (1), ##STR2## wherein m1=0,1 or 2, m2=0, 1 or 2, with the constraint that m1 and m2 are not to besimultaneously 0 or simultaneously 2; n1=2-m1, n2=2-m2; R=either H oralkyl with 1 to 8 carbon atoms, R'=alkyl with 1 through 18 carbon atoms,and X=H or OH.

The compounds of this invention may be mon-, di-, or tri-ester ofdiphosphonates, or a mixture of the three, with the di-ester ofdiphosphanates being the preferred product.

The "R" in the formula (1 ) is preferred to be H or a linear/branchedalkyl with 1 through 6 carbon atoms, and more preferred to be an alkylwith 1 through 3 carbon atoms, methyl for instance.

The "R'" in the formula (1 ) is preferably a linear/branched alkyl with6 through 14 carbon atoms, and even more preferably, a branched alkylwith 8 to 12 carbon atoms, like 2-ethyl-hexyl.

The "X" in the general formula (1) is preferably OH.

A process for producing the said diphosphonate compounds of the generalformula (1), ##STR3## wherein the definitions of m1, m2, n1, n2, R, R'and X are the same as above, consists of the steps of dissolving incertain solvent the solid phosphinic acids designated by the generalformula (2), ##STR4## wherein R and X are defined as in the formula (1),and adding under normal pressure the solution of diphosphinic acids thusobtained into an alcohol designated by the general formula (3),

    R'OH                                                       (3)

wherein the R' is defined as in the formula (1), where esterificationreaction will take place and the substances designated by the generalformula (1) will be obtained.

The diphosphinic acids of the formula (2) are preferred to be thosewherein R is H or an alkyl with 1 through 6 carbon atoms and morepreferred to be those wherein R is an alkyl with 1 through 3 carbonatoms, such as methyl, and X is OH. The alcohols of the formula (3) arepreferred to be those wherein R' is an alkyl having from 6 to 14 carbonatoms and more preferred to be those wherein R' is a branched alkylhaving 8 through 12 carbon atoms, for example, 2-ethyl hexyl. Both thediphosphinic acids of the formula (2) and the alcohols of the formula(3) are available on the markets.

The esterification temperature may range from 150° C. to 200° C.,preferably from 160° C. to 170° C.

The solvent for dissolving the diphosphinic acids may be selected frommethanol, ethanol and water, with water being the preferred.

It is recommended that the diphosphinic acids be poured into an alcohol,under stirring, gently in order to raise the yield.

Another aspect of the present invention relates to a compositioncontaining the diphosphonates of this invention.

The composition is composed of the diphosphonate compounds of thisinvention and one or several transitional metal salts, of which molarratio ranges between 1:1-20, preferably 1:3-10.

The transitional metals thereof may be selected from the salts ofcobalt, copper, manganese, vanadium, chromium and molybdenum, or theirmixture, with cobalt as the one preferred.

The composition may be prepared by simply mixing the diphosphonatecompounds with the transitional metal salts.

The compounds of the present invention may be used alone or in the formof composition for oxidation of hydrocarbons such as the catalyzedoxidation of cyclohexane, oxidations of p-xylene and of paraffins.

There are primarily two processes hitherto known in industries foroxidation of hydrocarbons: organic salt-catalyzed oxidation in liquidphase and non-catalyzed oxidation. The diphosphonate compounds of thepresent invention will, when used, improve both processes.

In the case of non-catalyzed process, the diphosphonate compounds of thepresent invention, when added, will curb the side-reactions and raisethe yield accordingly.

In the case of catalyzed process, adding of the compounds of the presentinvention improves the catalyzing activity of relevant metal ions andlessens deep oxidation, preventing cake-forming and hence extendingcontinuous production period, and as a result, the yield goes up.

The amount of the compounds of the present invention added as aco-catalyst may vary from 0.01 to 10 ppm and preferably from 0.05 to 5ppm.

The composition of the present invention may also be directly added as acatalyst in the case of catalyzed process, the concentration of whichmay range from 0.1 to 100 ppm per total feeds, preferably from 0.5 to 10ppm.

The compounds of the present invention and composition containing themas catalysts are especially suitable for commercial operations of thecyclohexane oxidation. With the current use of conventional cobalt-basedcatalyst, the molar yield is always below 80 per cent and cake-formingsevere. Moreover, when pyrophosphate is spread over the walls, theproduction can run only about two months before being forced to shutdown for cleaning cake-deposits, which causes not only interruption ofproduction, but serere environmental pollution as well.

In contrast, without the need for changing in process parameters ofcobalt catalyzing and equipment, the diphosphonate compounds of thepresent invention is capable of improving the catalyst activity ofcobalt ion for the oxidation of cyclohexane, lessening deep oxidations,stopping the heavy build up of cakes and equipment plug, extending theperiod of non-stop running and raising the yields for alcohols andketones.

In the case of the cyclohexane oxidation, the dosage of the compounds ofthe present invention may vary from 0.01 to 10 ppm and preferably from0.5 to 5 ppm; whereas when the composition of the present invention isused, the dosage ranges from 0.1 to 100 ppm, preferably from 0.5 to 10ppm.

In addition, the diphosphonate compounds of the present invention mayalso be used as a complex-extracting agent for metal ions and coagulantfor epoxy resin.

The following are examples which are quoted here merely to illustratesome aspects of the present invention and they by no means limit thescope of this invention.

EXAMPLE 1

3,500 ml of 2-ethyl hexanol was poured into a 5,000 ml three-neckedflask heated with hot plate at the bottom and stirred by bubblingnitrogen through the contents. At the top of the flask, a decanter and acondensing coil of ball type were mounted with cooling water circulatingthrough the jacket of the coil. When the temperature reached 160° C.,HEDP (i.e. 1-hydroxy-ethylidene-1,1-diphosphinic acid rs, similarlyhereinafter) solution was gently added. While both 2-ethyl hexanol andwater were boiling (azeotropism), the vapor flowed through the coilwhere it condensed, and into the decanter where water was taken out ofthe system from the bottom and the top layer, 2-ethyl hexanol condensaterecycled back to the reactor. The amount of solid HEDP in the solutionthat was added into the system for each batch was 1,100 g. The feedinghad lasted for some 2 hours before the system was held under reflux for30 minutes until all the resultant water was bled off. After reaction,about 4,000 ml crude product was obtained in the flask. When cooleddown, the product so obtained was rinsed with equal amount of water, and4,000 ml of cyclohexane was added. Having settled, the contents splitinto two layers: in the bottom one there was a small amount of unreacteddiphosphinic acids and sulfuric acid (catalyst); the top layer--an oillayer, was then distilled in vacuum where water, cyclohexane and 2-ethylhexanol were removed from the top, and at the bottom, about 2,000 g ofproduct, was obtained.

The melting point of the product is -39° C., and the decompositiontemperature--215° C. The results of a series of tests usingfield-decomposition mass spectrum (FDMS), infra-red spectrum (IR) andnuclear magnetism resonance (NMR), etc. proved that the principalcomponent was di-2-ethyl-hexyl 1-hydroxy-ethylidene-1,1-diphosphonateester with only small amounts of mono-2-ethyl-hexyl1-hydroxy-ethylidene-1,1-diphosphonate ester, tri-2-ethyl-hexyl1-hydroxy-ethylidene-1,1-diphosphonate ester, and 2-ethyl hexanol asimpurities. The di-2-ethyl-hexyl 1-hydroxy-ethylidene-1,1-diphosphonateester has been proven to be a new compound (see below).

IR: 1017 cm, 1218 cm, 1380 cm, 1463 cm etc.

NMR: 0.83 ppm, 1.24 ppm, 3.95 ppm.

FDMS m/Z: 341 [M1+Na], 453 [M2+Na], 565 [M3+Na], wherein

M1=mono-2-ethyl-hexyl 1-hydroxy-ethylidene-1,1-diphosphonate ester

M2=di-2-ethyl-hexyl 1-hydroxy-ethylidene-1,1-diphosphonate ester

M3=tri-2-ethyl-hexyl 1-hydroxy-ethylidene-1,1-diphosphonate ester

EXAMPLE 2

As a comparative case with example 1, 3,500 ml of 2-ethyl hexanol and1,100 g of solid HEDP were added into a 5,000 ml three-necked flaskheated with hot plate at the bottom and stirred by bubbling nitrogenthrough the contents. At the top of the flask, a decanter and acondensing coil of ball type were mounted with cooling water circulatingthrough the jacket of the coil. When the temperature reached between130° and 200° C., the liquid began to boil and reaction started, yetwith very slow rate of esterification. The results showed that only asmall amount of HEDP esters were yielded. It is believed that thepredominant reaction was, in fact, the dehydration of 2-ethyl hexanolwhich caused formation of a great amount of 2-ethyl hexene.

EXAMPLE 3

Also taken as a comparative case with example 1, 3,500 ml of light oilwhich had been taken as a by-product from the process of an oxidation ofcyclohexane for producing cyclohexanone, and mainly containedesterification-capable components including cyclopentanol, n-pentanoland cyclohexanol was poured into a 5,000 ml three-necked flask heatedwith hot plate at the bottom and stirred by bubbling nitrogen throughthe contents. At the top of the flask, a water decanter and a condensingcoil of ball type were mounted with cooling water circulating throughthe jacket of the coil. When the temperature reached 140° C. and theliquid began to boil, HEDP dissolved in water was gently added. Whileboth the light oil and water were boiling (azeotropism), the vaporflowed through the coil where it condensed, and into the decanter wherewater was taken out of the system from the bottom and the top layer--thelight oil condensate recycled back to the reactor. The amount of solidHEDP in the solution that was added into the system for each batch was200 g. The feeding had lasted for some 2 hours before the system washeld under reflux for 30 minutes until all the resultant water was bledoff. After reaction, about 3,500 ml crude product was obtained in theflask. When cooled down, the product so obtained was rinsed with theequal amount of water, and 3,500 ml of cyclohexane was added. Havingsettled, the contents split into two layers: in the bottom one there wasa large amount of unreacted diphosphinic acid and a little sulfuric acid(catalyst); the top layer--an oil layer, was then distilled in vacuumwhere water, cyclohexane and light oil were removed from the top and atthe bottom, only tiny amount of pentyl HEDP esters (approx. 10 g), theproduct, was obtained. The yield of useful diphosphonates was very poor.

EXAMPLE 4

3,500 ml of lauric alcohol was poured into a 5,000 ml three-necked flaskheated with hot plate at the bottom and stirred by bubbling nitrogenthrough the contents. At the top of the flask, a decanter and acondensing coil of ball type were mounted with cooling water circulatingthrough the jacket of the coil. When the temperature reached 160° C.first 50 ml of p-xylene was added and then HBDP(1-hydroxy-butenylidene-1,1-diphosphinic acid was gently added. Whilethe lauric alcohol, PX and water began boiling (azeotropism), the vaporflowed through the coil where it condensed, and into the decanter wherewater was taken out of the system from the bottom and the top layer--thelauric alcohol and PX condensate recycled back to the reactor. Theamount of solid HBDP in the solution that was added into the system foreach batch was 1,500 g. The crude product was rinsed, distilled andfinally, 2,400 g product, di-lauric1-hydroxy-butenylidene-1,1-diphosphonate ester was obtained by thefollowing equation: ##STR5##

EXAMPLE 5

100 ml of benzene was added to a 250 ml separating funnel and then 1 gof cobalt cycloalkanoates was added, which was evenly suspended in thebenzin phase and the cobalt ions were extracted into water phase lateron after 100 ml of 2% solution of hexane diacid was added. At thispoint, 1 g of di-2-ethyl-hexane HEDP ester was added, and the cobaltions in the water phase below were extracted back to the oil layerabove.

EXAMPLE 6

50 g of epoxy resin of general purpose, while being stirred, was mixedwith 5 g of dilauric HBDP ester. After being heated for 40 minutes at atemperature between 160° and 200° C., the resin was perfectly fixed andmolded, with all the targets meeting the standards upon tests.

EXAMPLE 7

This is a comparative case with example 8 that follows, in an industrialunit for producing 8,000 t/y of cyclohexanone by cobalt-catalyzedoxidation of cyclohexane, sodium pyrophosphate was spread over the wallsof reactors for deactivation. The feed of cyclohexane was 36 m³ /h; andair flow 2,100 Nm³ /h. Cobalt salt in the form of cycloalkanoates incyclohexane solution was fed into the system continuously; theconcentration of cobalt ions in the oxidation system was controlled at0.26 ppm by weight, or 2 Kg of cobalt cycloalkanoates (about 8% ofcobalt ions) mixed in 2 m³ of cyclohexane each day. The amount ofprepared 2 m³ of cobalt salt in cyclohexane solution was metered and fedout by metering pumps into No. 1 oxidation reactor continuously at afixed rate over 24 hours. The system pressure was controlled at 1MPa.g.; reaction temperature--154+/-2° C. the process of oxidation ofcyclohexane went smoothly. The off-gas from the oxidation contained 2.5%of oxygen, when sampled with a glass sampling bottle. By visual exam,the samples looked turbid, with a small amount of yellow brown liquid atthe bottom and some particles of the same color sticking to the walls ofthe bottle. After subsequent processes: saponification, distillation ofoxidized products, and dehydrogenation of cyclohexanol, etc., an averageoutput of 27.1 t/d of cyclohexanone was obtained at a consumption ofcyclohexane--33.1 t/d. After about 2 months continuous running this way,the operation was forced to shut down for 48 hours to clean the systembefore resuming, because of heavy deposits that occurred inside thereactors and connecting piping, causing eventually system plugged.During the cleaning, the reactors and piping were flashed with a largeamount of soda water combined with manual cleaning of the deposits.

EXAMPLE 8

It is a case adopting the composition as a catalyst in an industrialunit for producing 8,000 t/y of cyclohexanone by cobalt-catalyzedoxidation of cyclohexane, the same unit as of example 7, but withoutusing sodium pyrophosphate as a deactivator. The feed of cyclohexane wasstill 36 m³ /h; and air flow 2,100 Nm³ /h. Cobalt salt in the form ofcycloalkanoates mixed with diphosphonates in cyclohexane solution wasfed into the system continuously; the concentration of cobalt ions inthe oxidation system was controlled at 0.26 ppm by weight, and the molarratio between cobalt ions and the diphosphonates was 7:1, or 2 Kg ofcobalt cycloalkanoates (about 8% of cobalt ions), together with 150 mlof the diphosphonates, mainly di-2-ethyl-hexane HEDP ester mixed in 2 m³of cyclohexane each day. The amount of prepared 2 m³ of cobaltsalt/diphosphonates in cyclohexane solution was metered and fed out bymetering pumps into No. 1 oxidation reactor continuously at a fixed rateover 24 hours. The system pressure was controlled at 1 MPa.g.; reactiontemperature--154+/-2° C. The process of oxidation of cyclohexane wentsmoothly. The off-gas from the oxidation contained 2.0% of oxygen, whensampled with a glass sampling bottle. By visual exam, the samples lookedclear and bright, with a small amount of colorless liquid at the bottomwhich was proven to be an acid water, and only when oxidation conversionrate went high, some white particles, crystal hexane diacid, could befound sticking to the walls of the bottle. After subsequent processes:saponification, distillation of oxidized products, and dehydrogenationof cyclohexanol, etc., an average output of 30.2 t/d of cyclohexanonewas obtained at a consumption of 34.7 t/d of cyclohexane. When comparedwith example 7, the output per unit time went up by 10% and total yieldup by 5% respectively. After one year's continuous running this way,there was still no sign of deposits in either reactor or piping. Theoperation would have been kept going, had there not been an annualscheduled shut down for maintenance. When opened without any cleaning,no deposits, what so ever, was found inside the equipment or pipingsystem and the walls inside were shining as they had been originally. Itcan be ascertained that the unit as it was may be continuously run forat least one year.

EXAMPLE 9

In conventional process of non-catalyzed oxidation of cyclohexane forproducing cyclohexanone/cyclohexanol, sodium pyrophosphate is used as adeactivator to spread over the walls of reactors, which will bring insodium ions which, in turn, will accelerate the side reactions causingpoor yield. This time, in the same unit, all process parameters werekept unchanged except that instead of spreading sodium pyrophosphate onthe walls, a small amount of diphosphonates, mainly di-2-ethyl-hexaneHEDP ester, was continuously fed into No. 1 reactor of the oxidationsystem, with the concentration of diphosphonates in the reactantscontrolled at 0.3 ppm by weight; and there was no more deposits in thesystem. In addition, the oxidation product turned less colored and theside reaction depressed. The result was reflected on 2% increase in thetotal yield of alcohol/ketone products.

EXAMPLE 10

In conventional processes of paraffin oxidation producing higheralcohols/ketones, for instance, in the process of oxidation of C12through C18 paraffins for producing C12 through C18 alcohols, the sameproblems of fouling and plugging in the equipment and piping are alsopuzzling the normal operation. However, when such an amount ofdi-2-ethyl-hexane HEDP ester was put into the feed stream that theconcentration was kept at around 0.3 ppm by weight, or the molar ratiobetween catalyst metal ions and diphosphonates at 5 to 1, the paraffinoxidation reactors were free from deposits and the usable product yieldwent up by 3%.

EXAMPLE 11

In a commercially operated unit for producing 1,000 t/y of p-toluic acidby the oxidation of p-xylene, the same problems of fouling/plugging inequipment/piping exist. Only such an amount of di-2-ethyl-hexane HEDPester was put into the feed stream that the concentration was kept atanywhere between 0.5 ppm and 3 ppm by weight, while allprocess/equipment parameters were kept unchanged includingcobalt-catalyst concentration, reaction pressure, temperature, feed andair flow, etc., no more deposits was found in the reactor and the totalyield of target product, p-toluic acid, went up by 3 percent.

I claim:
 1. A method for the transition metal ion salt-catalyzedoxidation in liquid phase or the non-catalyzed oxidation in liquid phaseof paraffin, cycloalkane or aralkane hydrocarbons to form alcohols andcarbonyl compounds in which the said oxidation is carried out in areaction system containing from 0.01 to 100 ppm per total feeds of adiphosphonate compound having the following formula: ##STR6## wherein m₁=0,1 or 2; n₁ =2-m₁ ; m₂ =0,1 or 2; n₂ =2-m₂ ; 0<m₁ +m₂ <4; R is H oralkyl having 1-8 carbon atoms; R' is alkyl having 1-18 carbon atoms; andX is H or OH.
 2. The method according to claim 1 wherein R' is alkylhaving 6-14 carbon atoms, and R is H or alkyl having 1-6 carbon atoms.3. The method according to claim 2 wherein X is OH; R' is branched alkylhaving 8-12 carbon atoms; and R is alkyl having 1-3 carbon atoms.
 4. Themethod according to claim 3 wherein R' is 2-ethylhexyl; R is methyl; andm₁ and m₂ are both
 1. 5. The method according to claim 1 wherein thehydrocarbon is cyclohexane.
 6. The method according to claim 1 whereinthe amount of the diphosphonate compound used is from 0.01 to 10 ppmbased on the weight of the hydrocarbon in the oxidation reaction system.7. The method according to claim 1 wherein the amount of the compoundused is from 0.05 to 5 ppm.